const emailReg = /^([A-Za-z0-9_\-\.])+\@([A-Za-z0-9_\-\.])+\.([A-Za-z]{2,4})$/
const emailStrWY = '956666@163.com';
const emailStrQQ = '956666@qq.com';
console.log(emailReg.test(emailStrWY)); 
console.log(emailReg.test(emailStrQQ));
const test = '1231242344123123123123123@qq.com';
console.log(emailReg.test(test));
const noEmail = '72873213.com';
console.log(emailReg.test(noEmail)); 